Still image taken from video shows Police vehicles at the scene near where a French police commander was stabbed to death in front of his home in the Paris suburb of Magnanville, France, June 14, 2016. REUTERS/Reuters TV

Still image taken from video shows Police vehicles at the scene near where a French police commander was stabbed to death in front of his home in the Paris suburb of Magnanville, France, June 14, 2016. REUTERS/Reuters TV

Still image taken from video shows Police vehicles at the scene near where a French police commander was stabbed to death in front of his home in the Paris suburb of Magnanville, France, June 14, 2016. REUTERS/Reuters TV

Still image taken from video shows Police vehicles at the scene near where a French police commander was stabbed to death in front of his home in the Paris suburb of Magnanville, France, June 14, 2016. REUTERS/Reuters TV